Coreflooding is one of the principal tools through which we qualify drilling and completion fluids and assess the potential for formation damage, but is it relevant? By “relevant,” I mean does it give an accurate portrayal of the likely performance of the selected fluids in terms of potential damage and how effectively a well will clean up? These are important considerations, but can they be derived from a core plug that is representative of the main production interval and is used in a coreflood test where one of the main results obtained is a return permeability (the difference between the initial and final permeability after fluid exposure)? In reality, most use of coreflooding is in the selection of the optimal drilling and completion fluids on the basis of comparison of the return permeabilities. Many coreflood procedures use, for example, a standard sequence of drawdowns after exposure of the plug to drilling and completion fluids to represent cleanup without considering actual well conditions and expected flow rates. Are such core-floods relevant, or could we be discarding fluids that could function quite well if field-relevant coreflood testing conditions had been selected?

Are there instances where performing coreflooding is not relevant? Can the same mud formulation that has been tested and qualified for one field be used on an adjacent field where the reservoir type and conditions are similar? A thorough evaluation needs to be performed before making any decision, and there can be cases where additional coreflooding could be deemed unnecessary. How about the case where there has been a change to a mud formulation that has already been qualified by coreflooding (e.g., base oil has been changed with another or change to the emulsifier package)? Should the new formulation be requalified through coreflooding?

There are many questions here to think over; however, consider the first question: “Is coreflooding relevant?” Yes, it is. We will be discussing this topic along with others at the Friday Forum of the SPE International Conference and Exhibition on Formation Damage Control, 7–9 February, in Lafayette, Louisiana. Come along!